Flexibilizing rigid foams



June 29, 1965 MAsAo NAKAMURA 3,191,224

FLEXIBILI Z ING RIGID FOAMS Original Filed May 31, 1952 3 Sheets-Sheet l a Q F K s I@ 4 449 QM @MJ 87,9 44g 376)) f 16 INVENTOR Mama@ /Vaama/"a June 29, 1965 MASA@ NAKAMURA 3,191,224

FLEXIBILIZING RIGID FoAMs Original Filed May 31, 1962 A 5 Sheets-Sheet 2A INVENTOR.

)Fn M0500 Nakamura June 29, 1965 MAsAo NAKAMURA 3,191,224

FLEXIBILIZING RIGID FOAMS Original Filed May 3l, 1962 3 Sheets-Sheet 3 125A In INVENTOR. Masa@ Nakamura HGENT United States Patent O 3,191,224 FLEXIBILIZING REGIE FOAMS Masao Nakamura, Midland, Mich., assigner to The Dow Chemical Company, Midland, Mich., a corporation of Delaware Original application 'May 31, 1962, Ser. No. 198,824.

Divided and this application Ilan. 2, 1964, Ser.

4 Claims. (Cl. 18-1) This application is a division of Serial Number 198,824, tiled May 3l, 1962.

This invention relates to a method and apparatus for ythe flexibilizing of rigid plastic foam, and more particularly relates to a ethod and apparatus which will confer directional flexibility on rigid plastic foams.

` The term directional ilexibility refers to the property of materials to bend in one direction or about any one of a number of parallel lines disposed in a plane. Typically, a number of wooden boards in closely adjacent relationship and having a hinge between each adjacent member will be iiexible only when bent in a direction substantially at right angles to the hinge direction. The term rigid plastic foam refers to those plastic foams such as are prepared from polystyrenes, polyurethanes, and the like which tend to rupture and break if a sheet of such material is bent about a radius which is approximately ten times the thickness of the sheet or smaller and yet permit some viscous flow of the polymeric material under stress. Rigid plastic foams are particularly desirable in applications where compressive strength is necessary as well as in cases where the foam constitutes an actual mechanical element of the structure and is utilized for load bearing or similar purposes.

Frequently, it would be convenient to utilize the structural benefits which can be derived from rigid foams in many applications, particularly in packaging and as cores for foamed plastic structures such as cylinders and similar geometric forms developed by bending a plane. Frequently, the bodies of rigid plastic materials having such shapes are constructed by a molding or piecing together of flat planks. Such operations are undesirable and often an inconvenience, particularly in instances where there `is insufficient demand for the particular articles to warrant the use of mass production techniques in their preparation.

It is an object of the present invention to provide a method of exibilizing a rigid plastic sheet It is a further object of this invention to provide an apparatus which will continuously prepare iiexibilized plastic sheets.

1t is another object of this invention to provide a method and apparatus which will continuously produce a iiexibilized plastic sheet by continually crushing a foamed plastic sheet in one direction.

These benefits and other advantages are achieved in accordance with the invention by partially crushing a cellular or expanded plastic body in a direction generally normal to the direction of the desired liexibility.

Flexible foam plastic sheet is readily prepared by an apparatus in accordance with the invention which comprises a means to forward a foamed plastic sheet, a means to retard the forwarding of said foamed plastic sheet, said means to retard the forwarding of said plastic sheet adapted to permit the advancement of the foamed plastic sheet at a rate less than the means to advance said plastic sheet, said means to advance the plastic sheet being positioned closely adjacent to said means to retard said plastic sheet and adapted to partially crush said foamed plastic sheet between said means to advance said plastic sheet and said means to retard said sheet.

The success of the method and apparatus of the present "Ice invention appears to be based on the controlled introduction of wrinkles into the cell walls of the plastic foam without the rupturing of a significant number of the cells.

Other objects and advantages of the invention will become more apparent from the following description when taken in conjunction with the accompanying drawing wherein:

FIGURES 1, 2 and 3 represent three views of an apparatus in accordance with the invention for the flexibilizing of rigid foam plastic sheet.

FIGURES 4. 5, 6, 7, 8 and 9 depict the operation of the apparatus shown in the FIGURES l-3.

FIGURE l0 depicts a front view of an alternate embodiment of a sheet flexibilizer in accordance with the invention.

FIGURE ll shows a partly-in-section view of the apparatus of FIGURE 10 in engagement Wtih the rigid foam plastic sheet being tlexibilized.

In FIGURES l, 2 and 3, there is illustrated a rigid foam ilexibilizing apparatus generally designated by the reference numeral 10. The apparatus 10 comprises a bed 12. The bed 12 is made up of a bed plate 14 having fixed thereto mounting brackets 15, 16 and 17. Mounted between the base plate 14 and the bracket 16 is a side plate 18 and mounted between the bracket 17 and the base plate 14 is an oppositely disposed side plate or bracket 19. Portions of the side plates 18 and 19 are connected to and braced by a frame member 21. Within the side plates 19 and 18 generally adjacent the brace member 21 is disposed a pair of bearing means 23 and 24, respectively. The bearing means 23 and 24 rotatably support a shaft 26, the shaft 26 in turn carries an operating cam 28, a second matched operating cam 29. The cams 28 and 29 are disposed between the side plates 18 and 19. The shaft 26 is provided with an operating means 31 and external to the side plate 18 is provided with a cam 33. Also external to the side plate 19 is mounted a positioning cam 35 adjacent to a sprocket 37. A reciprocally pivoting shaft 38 is supported from bearing 40 and 41 positioned in the side plates 18 and 19. The reciprocally pivoting shaft 38 supports a foam gripping shoe 44. The shoe 44 is connected to the shaft 38 by means of the ann members 46 and 47 and by means of the cap screws 48 and 49. The shoe 44 is spaced from the arms 46 and 47 by means of the spacers 50. Disposed immediately below and adjacent to the foam gripping shoe 44 is a stationary foam gripping shoe 52. External to the side plates 18 and 19 and mounted on the pivots 53 and 54 are disposed a pair of lever members 55 and 56, respectively. The lever members 55 and 56 are inoperative engagement with cam members 33 and 35, respectively, and are maintained in engagement therewith by means of the springs 57 and 58. The pivot points of 53 and 54 are adjustably mounted to the side plates 18 and 19, respectively, in order that the engagement between the cam 33 and the lever 53 and cam 35 and lever 55 may be varied at will. The end of the lever of 53 opposite to the end engaged by the spring 57 is pivotally connected to a push rod 60 and the lever 55 is similarly pivotally connected to a push rod 61. The push rods 60 and 61 are operatively connected to a sliding foam gripping assembly generally designated by the reference numeral 65. The assembly 65 is slidably mounted upon the base plate 14. The assembly 65 comprises a pair of side frameplates or members 67 and 68. The side plate 67 engages the bed plate 14 and is maintained in position by means of the ways 69 and 70. The side plate 68 is similarly maintained in position by means of the upper way 72 and a way 73 disposed on the opposite side of the bed plate 14. The side plates 67 and 68 are maintained in spaced relationship by means of a rotating shaft 75 which connects to the side plates 67 and 68 by the bearing means s Y 77 and 78, respectively. Alignment of the side plates 67 and '68 is further maintained by the brace member 80 and an oscillating shaft 82. The assembly`65 is substantially i similar in operation and constructionto the hereinbefore described foam gripping means with thefexception that -itis slidably mounted-'entire bed 14. The shaft 82 has vrigidly Aatlxed thereto a pair of Yarms y84 fand-85 which tudinal direction when the loading is applied normal to the major, face. 'j However the` sheet4 is exible and Lare inoperative 'engagement Vwithrthe reciprocating foam gripping shoe 87 .and is rigidly supportedbetween`V the frame-members@ and'68. A-iixed foam gripping shoe 88 is disposed below shoe 87. The arms 84y and S5 are 'activated by a pair `of'cams `89and90, `which are supported Y on'the shaft 7'5. The shaft 75'Ufurther `carries a ,sprocket `may readily be .bent Vabout a radius which may be less f thanthe thickness of the, sheet itself.;Y In thel transverse direction, the strength of the sheetis substantially unchanged andthe `stiffness retained. Similarly, edge loadl 'ing of abody which is crushed in accordance with rthe 97. The assembly 65 is adjustably aiii'xed to the actuating i rods 60 and Y61 by means of and 100. K d j Pivotally supported from the-shaft 38 is an arm V102- y'the rod engaging ears 99 2 fand 3, shaft'26 is yrotated by 'the operating means of'31 and roller chain l'6causes thersprocket 97 to-rotate and, consequently, the shaft 75 with lits Vvassociated cams are rotated. Cams 33 and 35^engage the operating levers Vwhich is rotatably mounted at the endthe'reo'f, and gen# 55 and 56 which, in turn, actuate the push rodsf60 and 61 causing the assembly 65 tooscillate on the bed plate 14.

Rotation tof the `cams y28 and 29 on the shaft 26 cause the Afoam grippingplate 44 to execute an oscillating function with 4respect tor the oppositely 'disposed Vfoam gripping fplate A52.Y Similarly, rotation of 'theshaft 75 and the Jcams 89-and 90 cause the foam gripping plate87'to ap-A proach and withdraw fromthe 'foam gripping plate 88.'

The mechanical lsequence `of operation is best understood by reference to FIGURES '4, 5,6, 7,' 8 'and V9, vwherein invention indicates that the strength in this direction -has not been overly altered., c

vA second embodiment ofY the invention is illustrated Y in :FIGURES 1.0 and '11." FIGURE 10 represents la front view of a foam 4flexibilizer and FIGURE 11 is a partly-in-sectionzview. The foam 'flexibilizer .is generally `"designated bythe reference numeral 120 'and comprises two pairs ofrspaced'rolls, the rolls are 121, '12141, 122'and 201122@Y The rolls 121, 121a, 122and `122a are supported by means'o'fjan adjustable :frame i123 .whereby the spac- -ing 124l between adjacent rolls is readily adjusted. For this purpose, there are "provided threaded spacing (mem- "bers 126 vwhich serve 'tov'a'rythe distance between the froll ycenters by varying thejdis'tance between the frame parts 123 and 12351.4V The roll 122e fis driven by a driv- 'fing meansf12'7 inthe direction indicated by. the arrow. A gear. 4129is providedv attachedtofthe roll 122:1, which, 4in turn,1engages kan idler gear '130 which is aiiixed to the iframe 123. The "idler, gear 130 is in operative engagement withrthe gear'133 tired to the roll 121:1. The ratio between the Vgears A1291and 133is such that the `roll 12111 is rotating "in the same direction as [roll 122but at a higher surface velocity. The roll 12111, in cooperation with roll 1721, serves to forward rigid `foam plastic Vsheet introduced into lthe space l125 Ybetween the'rolls 121 and .121a. Plastic 4the lsequential steps of the operation are schematically 4illusrated. In 'FIGURE 4, foam gripping .'jaws are schematicallydepictedand identied bythe'referen'ce numer- -als 44a, '52a, 87a and y88a.. V'A' sheetof rigid "foam Vbeing -ilexibilized is between -the 4jaws and is'designated bythe `reference Vcharacter The jaws 44a 'and 5211?(equiv`alert ftotheA jaws '44 Vand '52 of FIGURES 1, 2 and 3) are in operative engagement with the s'heetoffoam material F. The jaws 87a and 88a are spaced from each otherand spaced from'the jaws-44a and 52a. VThe arrow designates that'the jaw 87a is moving toward thesheet f In-FIGURE 5, Athe 'jaw87'a has engaged the .foam F,

fthe pair vof jaws 87a and 88a gripping thefoam vF-are movedtow'ard the jaw pair 44a and 52a as indicated by the arrow. i

:of travel. The crossfhatched lportion ofthe 'foam sheet F, designated as F', representsfa portion of .the foam which has beenlongitudinally crushed. lThe arrow in 'dicates the movement of the'jaw 44a whereby the Vsheet F will be released. In FIGURE 7, `thejaw 44a has released the "sheet F and the/portion of n the sheet F Yhas expanded byits 'natural resiliency into the space between the jaw ,portions 44a and 52a, 'imparting a Vforwarding action to a portion of thesheet'F. The arrow indicates the jaw 44a is closing upon thesheet.

In FIGURE 8, the `jaw pair 44a and 52a are shown in engagement with Vthe'sheet "F 'in 'af portion of the crushed section `F. The direction of'motion ofthe foam engaging 'plate 87a 'is illustrated by the arrow.

In FIGURE 9, the jaw'87a is disengaged completely 'frotn'the foam sheet F andis moving toward the position ofthe jaws shown in FIGURE 4, whereuponthe ycycle is resumed.

y-sheet 4then enters the 'spac'e between .the rolls 122 and 122a which servesto gripthe vsheets .and prevent any move 4ment A'thereof other than that dictated by the roll sur- `face. Cooperative action "of the two roll pairs are such vthat a sheet entering the roll pair '121 and 121a is dis 'charged from he rolls 122 and 1'22a at a rateslower than 'the sheet enters. This compactingaction causes the foam `plastic sheet to Ybe crushed in aA longitudinal direction and becomeflexible. Therapparatus offthe invention, as ldepicted in FIGURES 10 and 11, permits the continuous iiexibilizing of rigid thermoplastic sheets without em- "ploying la reciprocatingmotion. f

The Aembodiment of the "invention, as illustrated `in `FIGURES( 10 and, 1.1, is particularlyadapted to the crushing of relatively 'light foam Yplastics and those that have the relatively lowibulk vdensity and subsequently have "little physical strength. If the lforce required yto crush a `sheet of foam is relatively large, the embodiment of FIGURES 1-3 is particularly advantageous as the foam 'engagingshoes distribute the 'force over .a relatively large l'portion of the sheet surface, whereas 'the embodiment 0f V'FIGURES 10 and 11`is particularly adapted to lhandling I vto "exibilize Aafoar'ned polystyrene plank Y,approximately v The apparatus, as depicted in vFIGURES 1, 2 and 3.,

1 inch 'thick,-12 inches wide, and about A9 feet in length. The density of the ,polystyrene foamplank wasv about 2V pounds .per vcubic vfoot Iand, thecell .sizey approximately 1 millimeter. The plank was iirst passed through the ap'- paratus, cut in half,` and one `'portion of the plank 'treated Aa second, time. The physical :properties of the .portion of the original plank were "determined of the plank after ybeingliexibilized in accordance Awith the invention after one pass and after being exibilized twice. The results obtained with a sample to determine the changes in density, thermal conductivity and compressive strength are as follows:

Sample A Density, Thermal Compressive lbs/cu. It. conductivity strength, p.s.i.

Original 1. 73 301 28. 6 One pass 2. 282 29 Two passes 2. 36 277 28 kwere also polystyrene foam of about 1 millimeter cell size, 1 inch 1n thickness and 12 inches wide. The results are set forth 1n the followmg tabulation.

Density Compressive Min. blending lbs/cu. it. strength, p.s.i. diameter before break, inches Sample B:

Original. 1.69 27. 3 One pass... 1. 78 Two passes. 1. 98 28 3 3.0 Sample C:

Original- 1. 59 25. 8 One pass.-. 1. 76 Two passes. 1. 91 28. 3 3. 5 Sample D:

Original- 1. 59 One pass--- 1.91 26 3.0 Sample E:

Original- 1. 66 One pass. 2. 04 25. 9 3. 0

Relatively high density polystyrene foam having a thickness of about 1/2 inch, width of about 12 inches, and a cell size of about 0.1 millimeter was subjected to one pass through the reciprocating iiexibilizer in a manner similar to the previous samples. The averaged results of several samples are as follows.

A sample of foamed polystyrene board having a density of about 1.8 pounds per cubic foot, one-half inch thick and having a cell diameter of about 1 millimeter was passed through a exibilizing apparatus substantially as shown in FIGURES 1, 2 and 3. The flexibilized sheet was bent through an angle of about 180, to form a bend which had substantially no internal radius without rupturing. A sample of the board which was not exibilized broke when bent to a radius of about 11 inches.

A further sample of a polystyrene board having a density of about 1.8 pounds per cubic foot, three-eighths of an inch thick, and having a cell size of from about 1.3 to about 0.5 millimeters was ilexibilized in accordance with the invention employing apparatus generally as shown in FIGURES 1, 2 and 3. The ilexiiied board broke when a bending radius of 0.65 inch was reached, whereas the untreated board broke when bent over a diameter of about six inches.

Similar beneficial results were obtained when foam planks below one-half inch in thickness were utilized from a rotary flexibilizer substantially as illustrated in FIGURES 10 and 1l wherein the rolls were provided with a knurled surface and had a diameter of about four inches. On passing a foam sheet through the apparatus, physical properties were found to be commensurate with those obtained with the reciprocating flexibilizer.

In a similar manner, other rigid expanded plastic sheets and bodies are rendered selectively exible. Typical materials which may be employed are polyurethanes, polyvinyl chlorides, polyvinylidene chlorides, phenol formaldehyde and like foa-ms. Advantageously, a somewhat spongy effect is obtained when a foam plastic sheet is first passed through a fiexibilizer in accordance with the invention and subsequently is passed through a second time whereby the direction of feed is disposed at substantially right angles to the rst pass. In this manner, a more flexible sheet is obtained which can, to limited degree, assume a compound curvature.

As is apparent from the foregoing specification, the apparatus and method of the present invention are susceptible of being embodied vw'th various alterations and modifications which may diifer particularly from those that have been described in the preceding specification and description. For this reason, it is to be fully understood that all of the foregoing is intended to be merely illustrative and is not to be construed or interpreted as being restrictive or otherwise limiting of the present invention, excepting as it is set forth and defined in the hereto appended claims.

What is claimed is:

1. An apparatus for the tlexibilizing of a cellular plastic cellular plastic sheet, said apparatus comprising a means to forward a cellular plastic sheet, a means to retard the forwarding of said cellular plastic sheet comprising a pair of generally opposed surfaces adapted to retract from and to engage adjacent surfaces of foam plastic sheet and while engaging the foam plastic to move relative to the means to forward the expanded plastic sheet, said means to retard the forwarding of said cellu lar sheet adapted to permit the advancement of the cellular sheet at a linear rate less than that of the means to advance said plastic sheet, said means to advance the plastic sheet being positioned adjacent said means to retard said plastic sheet, and so constructed and arranged so as to partially crush said plastic sheet in the plane of the sheet between said means to advance said plastic sheet and said means to retard said plastic sheet.

2. An apparatus in accordance with claim -1, wherein said means to forward a foam plastic sheet comprises a pair of generally opposed surfaces adapted to close upon and engage said foam plastic sheet and while engaging said sheet to move toward said means to retard said expanded plastic sheet.

3. An apparatus in accor-dance with claim 1, wherein said means to forward a foam plastic sheet comprises a pair of generally opposed surfaces adapted to retract and engage said foam plastic and while in closed position move toward said means to forward said expanded plastic sheet.

4. An apparatus for the exibilizing of a cellular plastic sheet comprising a first pair or jaws, said jaws having opposed foamed plastic sheet gripping surfaces, a second pair of jaws having opposed foamed plastic sheet gripping surfaces, said rst jaws and said second jaws being slidably disposed with respect to each other, said first jaw and second jaw each provided with jaw opening and closing means, in cooperative combination with said jaw opening and closing means a common jaw activating means adapted to close said iirst and second jaws upon a sheet of cellular plastic material disposed between said jaws, means to cause said first jaws and said second jaws to approach each other, means to open said iirst jaws,

' ing Vthe operation thereof land lVerash the? sheet in ak drec.-l

tion in the plane thereof. WI'LL'IVA'M J. 'STE'PHENSON, Primaryfxaminr. 

1. AN APPARATUS FOR THE FLEXIBILIZING OF A CELLULAR PLASTIC CELLULAR PLASTIC SHEET, SAID APPARATUS COMPRISING A MEANS TO FORWARD A CELLULAR PLASTIC SHEET, A MEANS TO RETARD THE FORWARDING OF SAID CELLULAR PLASTIC SHEET COMPRISING A PAIR OF GENERALLY OPPOSED SURFACES ADAPTED TO RETRACT FROM AND TO ENGAGE ADJACENT SURFACES OF FOAM PLASTIC SHEET AND WHILE ENGAGING THE FOAM PLASTIC TO MOVE RELATIVE TO THE MEANS TO FORWARD THE EXPANDED PLASTIC SHEET, SAID MEANS TO RETARD THE FORWARDING OF SAID CELLULAR SHEET ADAPTED TO PERMIT THE ADVANCEMENT OF THE CELLULAR SHEET AT A LINEAR RATE LESS THAN THAT OF THE MEANS TO ADVANCE SAID PLASTIC SHEET, SAID MEANS TO ADVANCE THE PLASTIC SHEET BEING POSITIONED ADJACENT SAID MEANS TO RETARD SAID PLASTIC SHEET, AND SO CONSTRUCTED AND ARRANGED SO AS TO PARTIALLY CRUSH SAID PLASTIC SHEET IN THE PLANE OF THE SHEET BETWEEN SAID MEANS TO ADVANCE SAID PLASTIC SHEET AND SAID MEANS TO RETARD SAID PLASTIC SHEET. 